We have an impressive understanding of the cascades of genes needed for the differentiation of vegetative cells Bacillus subtilis into spores or into competent cells. However, in contrast, our knowledge of these morphometric processes is quite limited. Combining modern techniques of quantitative microscopy with image analysis, we are mapping the distribution of structural elements in cells, and using fluorescent probes so as to determine the location within individual cells of the expression of particular sporulation and competence genes. This is enabling us to study sporulation by describing in detail the segregation and differential condensation of the nucleoids, and the formation of the asymmetrically located sporulation septum. We intend to study the mechanism of compartmentalization of gene expression between mother cell and prespore. It has been suggested that fusion of the sporulation septal membrane is a crucial event in establishing compartmentalized gene expression; this supposition will be tested. We will investigate the structural consequences of compartment-specific gene expression, and the process of engulfment of the prespore by the mother cell. Competence will be studied with the same methodology in order to characterize how about 10% (but no more) of the vegetative population decrease in density and become capable of taking up exogenous DNA. In addition fluorescent probes capable of detecting late gene products and transforming DNA will be used to describe the distribution of sites on the cell surface for the binding and uptake of DNA, and the gene products required to construct such sites.